1. Field of the Invention
The present invention relates to a grommet, in particular for mounting on a wire harness fitted in vehicles such as automobiles. More particularly, the invention relates to a “one-motion grommet” (or “one-way grommet”), which is installed by insertion into a through-hole of a vehicle body panel. The grommet of the present invention provides mechanical protection, as well as water and dust protection, for the wire harness at the insertion point of the through-hole.
2. Description of Background Information
It is already known to install a grommet on the wire harness leading from the engine compartment to the passenger compartment of an automobile. Such a grommet is mounted around the through-hole of the car-body panel/bulkhead. The car-body panel/bulkhead separates the passenger compartment from the engine compartment of an automobile. The grommet protects the wire harness passing through the through-hole and provides protection from water and dust, as well as sound insulation between the engine compartment and the passenger compartment.
Several grommets of this type have already been proposed. An example of such a grommet is described in Japanese Patent Application JP-A-2002-171645 filed by the present Applicant and shown in FIGS. 1A and 1B of the present application. The grommet 1 shown in FIG. 1A includes a tubular portion 2 having a gradually widening diameter (referred to as “funnel-shaped portion 2”) and a tubular portion 3 linked to the small-diameter end part of the funnel-shaped portion 2. A press-fit groove portion 4 is provided in the larger-diameter end part of the funnel-shaped portion 2. This press-fit groove portion is used for fixing the grommet in the car-body panel. The press-fit groove portion 4 includes a groove 4a. The groove 4a is defined by a vertical wall 4b (i.e. whose face is in a radial cross-sectional plane of the grommet) disposed at the side of the groove closest to the large-diameter end part, and an inclined wall 4c (the inclination being relative to the aforementioned radial cross-sectional plane of the grommet) disposed at the side of the groove closest to the small-diameter end part of the funnel-shaped portion 2. A plurality of rib portions 2a is provided on the external conical face of the funnel-shaped portion 2. These rib portions 2a extend from the top of the inclined wall 4c substantially to the part of the funnel-shaped portion 2 where the latter joins to the tubular portion 3. The wire harness W/H passes through the tubular portion 3 into the space inside the funnel-shaped portion 2. The wire harness W/H is then fixed by a tape T at the end section of the tubular portion 3.
The grommet 1 is also provided integrally with two auxiliary tubes (only one is shown in FIG. 1A, at the left-hand part just above wire harness). Each auxiliary tube has a first end led out through a respective cavity (not shown in the figure) formed between two ribs 2a, a section which pass through the inside of the funnel-shaped portion 2, and a second end which extends beyond the flared end. One of the auxiliary tubes is used for passing a washer hose and the other for passing a hood (bonnet) wire. The tips of the auxiliary tubes are initially closed, and they are cut off when the hose or cable is passed through.
The operation for installing the grommet into the through-hole H of the car-body panel is as follows. The tubular portion 3 of the grommet 1 is inserted into the through-hole H from the engine compartment side. When the funnel-shaped portion 2 abuts against the internal circular face of the through-hole H, the grommet 1 is pushed forcibly. The funnel-shaped portion 2 is thereby deformed until it is squeezed into the through-hole and passed therethrough. After passing the through-hole, the grommet recovers its shape. Accordingly, the inclined wall 4c and the vertical wall 4b are tightly adjusted on either side of the car-body panel P. The press-fit groove portion 4 of the grommet 1 is in this way installed in the through-hole H of the car-body panel P. During this operation, referred to as “one-motion operation”, only the rib portions 2a come into contact with the internal circular edge of the through-hole H. The contact surface is thus reduced compared to the case where the whole external face of the funnel-shaped portion 2 contacts the internal circular edge of the through-hole H. Consequently, the insertion resistance is lowered and operability is improved. Further, when the wire harness, installed in the through-hole H, is pulled towards the engine compartment, the free end portions of the rib portions 2a are pressed against the external face of the tubular portion 3. Movements of the tubular portion 3 are thus restrained. The press-fit groove portion 4 of the grommet 1 is then prevented from exiting out of the through-hole H. The fixing force of the grommet 1 is thus improved.
The one-motion grommet 1 shown in FIGS. 1A and 1B features good operability for installation into the through-hole of the car-body panel. At the same time, this grommet has the advantage of providing a high fixing force once installed in the through-hole. However, a wire harness sometimes has to include a water-trapping portion A in which the bundle of electrical cables constituting the wire harness is bound with a water-trapping agent 5. In such case, the grommets 1 of the prior art still have distinctive drawbacks.
For instance, when the above-mentioned water-trapping portion A is provided, it is enclosed in the tubular portion 3 and exerts an enlarging force on the latter. However, as the water-trapping agent 5 fills the space between the electrical cables W and then hardens, the tubular portion 3 loses its flexibility. Consequently, when the wire harness W/H extending from the tubular portion 3 is wired inside the passenger compartment and has to be bent, the harness portion contained in the tubular portion 3 cannot be used for that purpose. A specific space for disposing the tubular portion 3 has therefore to be envisaged in the passenger compartment.
Further, when the part of the funnel-shaped portion 2 projecting in the passenger compartment is long, a special space for the grommet is needed.
However, as the number of parts placed in a vehicle has increased greatly in recent years, there is little room for loading supplementary parts. Moreover, the wire harness passed through the body panel must often be wired by flexing, while the above part projecting in the passenger compartment has a long projection. Accordingly, when the wire harness is to be wired alongside a body panel, it needs a large space for making a loop.
Typically, when the wire harness exiting from the grommet is turned at a sharp angle, deformations are caused in the funnel-shaped portion installed in the through-hole, and the peripheral rim of that portion drifts away from the groove base lip, thereby breaking the sealing and allowing water penetration.
The grommet of the prior art may include one or more auxiliary tubes for a hood wire or cable, a washer hose or the like. These auxiliary tubes are typically slender and thus prone to bending, making it difficult to pass the washer hose or hood wire through these tubes. Even when the hose and/or wire is passed through, the auxiliary tubes are not sufficiently rigid to hold them straight. When an auxiliary tube is bent, water flow, for instance, can be blocked.